Back
Problem 1
What is apoptosis?
a. An experimental technique used to kill specific cells
b. Programmed cell death that is required for normal development
c. A pathological condition observed only in damaged or diseased organisms
d. A developmental mechanism unique to the roundworm C. elegans
Problem 2
In adult animals, ___________ are a source of undifferentiated cells that can divide to produce cells that can specialize.
Problem 3
What is a homeotic mutant?
a. An individual with a structure located in the wrong place
b. An individual with an abnormal head-to-tail axis
c. An individual that is missing segments
d. An individual with double the normal number of structures
Problem 4
A tool-kit gene is .
Problem 5
A friend is interested in isolating genes that are expressed solely in liver cells but only has access to skin cells. She asks you for advice on whether to start her studies. What will you say?
Problem 6
The following predictions ask you to consider how genetic regulatory cascades provide positional information. Select True or False for each statement.
T/F Mutation of a gene at one level of a regulatory cascade will affect the expression of genes at all levels of the cascade.
T/F Mutation of a gene that is expressed later in a regulatory cascade will affect a smaller region of the body than mutation of gene that is expressed early in the cascade.
T/F In the regulatory cascade used by Drosophila, a gene at one level of the cascade will be controlled only by genes at the level immediately above it.
T/F Genes that control the largest regions of the Drosophila embryo are not transcribed in the embryo.
Problem 7
What is the connection between genetic regulatory cascades and the observation that differentiation is a step-by-step process?
Problem 8
Which of the following provides the strongest evidence for the conservation of tool-kit genes?
a. Bicoid moved from one fly embryo into the posterior of another fly embryo causes the formation of two head regions.
b. Mutation of an unrelated gene in another species of fly has a similar effect to mutation of bicoid in Drosophila.
c. A mouse Hox gene can be used to take over the function of a mutated Drosophila Hox gene.
d. Sheep can be cloned by fusing a differentiated adult cell with an enucleated egg.
Problem 9
Imagine a situation in which a morphogen has its source at the posterior end of a Drosophila embryo. Every 100 µm from the posterior pole, the morphogen concentration decreases by half. If a cell required 1/16th the amount of morphogen found at the posterior pole to form part of a leg, how far from the posterior pole would the leg form?
a. 100 μm
b. 160 μm
c. 400 μm
d. 1600 μm
Problem 10
Some stickleback fish develop protective spines, and other stickleback fish are spineless. Spine development is controlled by the expression of a gene known as Pitx1. The spineless phenotype is due to a mutation in Pitx1 that results in no expression of Pitx1 during development in regions where spines would otherwise form. When scientists compared the Pitx1 coding sequence in spined and spineless fish, they found this sequence was the same in both types of fish. Propose plausible hypotheses for the location of this mutation and for how it alters spine development.
Problem 11
Type I diabetes is a form of diabetes that is due to the loss of insulin-producing cells of the pancreas. The potential of stem cells—in particular, induced pluripotent stem (iPS) cells—for therapy has gotten a lot of press.
What are iPS cells?
a. Cells taken from early human embryos
b. Cells taken from the pancreas of people without diabetes
c. Cells derived by de-differentiating specialized adult cells
d. Cells derived by differentiating pancreas precursor cells
Problem 12
Type I diabetes is a form of diabetes that is due to the loss of insulin-producing cells of the pancreas. The potential of stem cells—in particular, induced pluripotent stem (iPS) cells—for therapy has gotten a lot of press.
If researchers were attempting to stimulate the differentiation of iPS cells, which of the following would they most likely add to the cell-culture medium (the liquid surrounding the cells)?
a. Activin A, an extracellular signal protein
b. Sox-2, a transcription factor active in early development
c. Grb-2, an intracellular signal transduction protein
d. Lactase, an enzyme that catalyzes the breakdown of lactose